/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.scripting.groovy;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;

import groovy.lang.GroovyClassLoader;
import groovy.lang.GroovyObject;
import groovy.lang.MetaClass;
import groovy.lang.Script;
import org.codehaus.groovy.control.CompilationFailedException;
import org.codehaus.groovy.control.CompilerConfiguration;
import org.codehaus.groovy.control.customizers.CompilationCustomizer;

import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.lang.Nullable;
import org.springframework.scripting.ScriptCompilationException;
import org.springframework.scripting.ScriptFactory;
import org.springframework.scripting.ScriptSource;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.ReflectionUtils;

/**
 * {@link org.springframework.scripting.ScriptFactory} implementation
 * for a Groovy script.
 *
 * <p>Typically used in combination with a
 * {@link org.springframework.scripting.support.ScriptFactoryPostProcessor};
 * see the latter's javadoc for a configuration example.
 *
 * <p>Note: Spring 4.0 supports Groovy 1.8 and higher.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rod Johnson
 * @see groovy.lang.GroovyClassLoader
 * @see org.springframework.scripting.support.ScriptFactoryPostProcessor
 * @since 2.0
 */
public class GroovyScriptFactory implements ScriptFactory, BeanFactoryAware, BeanClassLoaderAware {

    private final String scriptSourceLocator;

    @Nullable
    private GroovyObjectCustomizer groovyObjectCustomizer;

    @Nullable
    private CompilerConfiguration compilerConfiguration;

    @Nullable
    private GroovyClassLoader groovyClassLoader;

    @Nullable
    private Class<?> scriptClass;

    @Nullable
    private Class<?> scriptResultClass;

    @Nullable
    private CachedResultHolder cachedResult;

    private final Object scriptClassMonitor = new Object();

    private boolean wasModifiedForTypeCheck = false;


    /**
     * Create a new GroovyScriptFactory for the given script source.
     * <p>We don't need to specify script interfaces here, since
     * a Groovy script defines its Java interfaces itself.
     *
     * @param scriptSourceLocator a locator that points to the source of the script.
     *                            Interpreted by the post-processor that actually creates the script.
     */
    public GroovyScriptFactory(String scriptSourceLocator) {
        Assert.hasText(scriptSourceLocator, "'scriptSourceLocator' must not be empty");
        this.scriptSourceLocator = scriptSourceLocator;
    }

    /**
     * Create a new GroovyScriptFactory for the given script source,
     * specifying a strategy interface that can create a custom MetaClass
     * to supply missing methods and otherwise change the behavior of the object.
     *
     * @param scriptSourceLocator    a locator that points to the source of the script.
     *                               Interpreted by the post-processor that actually creates the script.
     * @param groovyObjectCustomizer a customizer that can set a custom metaclass
     *                               or make other changes to the GroovyObject created by this factory
     *                               (may be {@code null})
     * @see GroovyObjectCustomizer#customize
     */
    public GroovyScriptFactory(String scriptSourceLocator, @Nullable GroovyObjectCustomizer groovyObjectCustomizer) {
        this(scriptSourceLocator);
        this.groovyObjectCustomizer = groovyObjectCustomizer;
    }

    /**
     * Create a new GroovyScriptFactory for the given script source,
     * specifying a strategy interface that can create a custom MetaClass
     * to supply missing methods and otherwise change the behavior of the object.
     *
     * @param scriptSourceLocator   a locator that points to the source of the script.
     *                              Interpreted by the post-processor that actually creates the script.
     * @param compilerConfiguration a custom compiler configuration to be applied
     *                              to the GroovyClassLoader (may be {@code null})
     * @see GroovyClassLoader#GroovyClassLoader(ClassLoader, CompilerConfiguration)
     * @since 4.3.3
     */
    public GroovyScriptFactory(String scriptSourceLocator, @Nullable CompilerConfiguration compilerConfiguration) {
        this(scriptSourceLocator);
        this.compilerConfiguration = compilerConfiguration;
    }

    /**
     * Create a new GroovyScriptFactory for the given script source,
     * specifying a strategy interface that can customize Groovy's compilation
     * process within the underlying GroovyClassLoader.
     *
     * @param scriptSourceLocator    a locator that points to the source of the script.
     *                               Interpreted by the post-processor that actually creates the script.
     * @param compilationCustomizers one or more customizers to be applied to the
     *                               GroovyClassLoader compiler configuration
     * @see CompilerConfiguration#addCompilationCustomizers
     * @see org.codehaus.groovy.control.customizers.ImportCustomizer
     * @since 4.3.3
     */
    public GroovyScriptFactory(String scriptSourceLocator, CompilationCustomizer... compilationCustomizers) {
        this(scriptSourceLocator);
        if (!ObjectUtils.isEmpty(compilationCustomizers)) {
            this.compilerConfiguration = new CompilerConfiguration();
            this.compilerConfiguration.addCompilationCustomizers(compilationCustomizers);
        }
    }


    @Override
    public void setBeanFactory(BeanFactory beanFactory) {
        if (beanFactory instanceof ConfigurableListableBeanFactory) {
            ((ConfigurableListableBeanFactory) beanFactory).ignoreDependencyType(MetaClass.class);
        }
    }

    @Override
    public void setBeanClassLoader(ClassLoader classLoader) {
        this.groovyClassLoader = buildGroovyClassLoader(classLoader);
    }

    /**
     * Return the GroovyClassLoader used by this script factory.
     */
    public GroovyClassLoader getGroovyClassLoader() {
        synchronized (this.scriptClassMonitor) {
            if (this.groovyClassLoader == null) {
                this.groovyClassLoader = buildGroovyClassLoader(ClassUtils.getDefaultClassLoader());
            }
            return this.groovyClassLoader;
        }
    }

    /**
     * Build a {@link GroovyClassLoader} for the given {@code ClassLoader}.
     *
     * @param classLoader the ClassLoader to build a GroovyClassLoader for
     * @since 4.3.3
     */
    protected GroovyClassLoader buildGroovyClassLoader(@Nullable ClassLoader classLoader) {
        return (this.compilerConfiguration != null ?
                new GroovyClassLoader(classLoader, this.compilerConfiguration) : new GroovyClassLoader(classLoader));
    }


    @Override
    public String getScriptSourceLocator() {
        return this.scriptSourceLocator;
    }

    /**
     * Groovy scripts determine their interfaces themselves,
     * hence we don't need to explicitly expose interfaces here.
     *
     * @return {@code null} always
     */
    @Override
    @Nullable
    public Class<?>[] getScriptInterfaces() {
        return null;
    }

    /**
     * Groovy scripts do not need a config interface,
     * since they expose their setters as public methods.
     */
    @Override
    public boolean requiresConfigInterface() {
        return false;
    }


    /**
     * Loads and parses the Groovy script via the GroovyClassLoader.
     *
     * @see groovy.lang.GroovyClassLoader
     */
    @Override
    @Nullable
    public Object getScriptedObject(ScriptSource scriptSource, @Nullable Class<?>... actualInterfaces)
            throws IOException, ScriptCompilationException {

        synchronized (this.scriptClassMonitor) {
            try {
                Class<?> scriptClassToExecute;
                this.wasModifiedForTypeCheck = false;

                if (this.cachedResult != null) {
                    Object result = this.cachedResult.object;
                    this.cachedResult = null;
                    return result;
                }

                if (this.scriptClass == null || scriptSource.isModified()) {
                    // New script content...
                    this.scriptClass = getGroovyClassLoader().parseClass(
                            scriptSource.getScriptAsString(), scriptSource.suggestedClassName());

                    if (Script.class.isAssignableFrom(this.scriptClass)) {
                        // A Groovy script, probably creating an instance: let's execute it.
                        Object result = executeScript(scriptSource, this.scriptClass);
                        this.scriptResultClass = (result != null ? result.getClass() : null);
                        return result;
                    } else {
                        this.scriptResultClass = this.scriptClass;
                    }
                }
                scriptClassToExecute = this.scriptClass;

                // Process re-execution outside of the synchronized block.
                return executeScript(scriptSource, scriptClassToExecute);
            } catch (CompilationFailedException ex) {
                this.scriptClass = null;
                this.scriptResultClass = null;
                throw new ScriptCompilationException(scriptSource, ex);
            }
        }
    }

    @Override
    @Nullable
    public Class<?> getScriptedObjectType(ScriptSource scriptSource)
            throws IOException, ScriptCompilationException {

        synchronized (this.scriptClassMonitor) {
            try {
                if (this.scriptClass == null || scriptSource.isModified()) {
                    // New script content...
                    this.wasModifiedForTypeCheck = true;
                    this.scriptClass = getGroovyClassLoader().parseClass(
                            scriptSource.getScriptAsString(), scriptSource.suggestedClassName());

                    if (Script.class.isAssignableFrom(this.scriptClass)) {
                        // A Groovy script, probably creating an instance: let's execute it.
                        Object result = executeScript(scriptSource, this.scriptClass);
                        this.scriptResultClass = (result != null ? result.getClass() : null);
                        this.cachedResult = new CachedResultHolder(result);
                    } else {
                        this.scriptResultClass = this.scriptClass;
                    }
                }
                return this.scriptResultClass;
            } catch (CompilationFailedException ex) {
                this.scriptClass = null;
                this.scriptResultClass = null;
                this.cachedResult = null;
                throw new ScriptCompilationException(scriptSource, ex);
            }
        }
    }

    @Override
    public boolean requiresScriptedObjectRefresh(ScriptSource scriptSource) {
        synchronized (this.scriptClassMonitor) {
            return (scriptSource.isModified() || this.wasModifiedForTypeCheck);
        }
    }


    /**
     * Instantiate the given Groovy script class and run it if necessary.
     *
     * @param scriptSource the source for the underlying script
     * @param scriptClass  the Groovy script class
     * @return the result object (either an instance of the script class
     * or the result of running the script instance)
     * @throws ScriptCompilationException in case of instantiation failure
     */
    @Nullable
    protected Object executeScript(ScriptSource scriptSource, Class<?> scriptClass) throws ScriptCompilationException {
        try {
            GroovyObject goo = (GroovyObject) ReflectionUtils.accessibleConstructor(scriptClass).newInstance();

            if (this.groovyObjectCustomizer != null) {
                // Allow metaclass and other customization.
                this.groovyObjectCustomizer.customize(goo);
            }

            if (goo instanceof Script) {
                // A Groovy script, probably creating an instance: let's execute it.
                return ((Script) goo).run();
            } else {
                // An instance of the scripted class: let's return it as-is.
                return goo;
            }
        } catch (NoSuchMethodException ex) {
            throw new ScriptCompilationException(
                    "No default constructor on Groovy script class: " + scriptClass.getName(), ex);
        } catch (InstantiationException ex) {
            throw new ScriptCompilationException(
                    scriptSource, "Unable to instantiate Groovy script class: " + scriptClass.getName(), ex);
        } catch (IllegalAccessException ex) {
            throw new ScriptCompilationException(
                    scriptSource, "Could not access Groovy script constructor: " + scriptClass.getName(), ex);
        } catch (InvocationTargetException ex) {
            throw new ScriptCompilationException(
                    "Failed to invoke Groovy script constructor: " + scriptClass.getName(), ex.getTargetException());
        }
    }


    @Override
    public String toString() {
        return "GroovyScriptFactory: script source locator [" + this.scriptSourceLocator + "]";
    }


    /**
     * Wrapper that holds a temporarily cached result object.
     */
    private static class CachedResultHolder {

        @Nullable
        public final Object object;

        public CachedResultHolder(@Nullable Object object) {
            this.object = object;
        }
    }

}
